package com.om.calculator;


public class RpnCalculator {
    OperandStack values = new OperandStack();
    
    public void enter(int value) {
        values.push(value);
    }

    public void add() {
        int rightOperand = pop();
        int leftOperand = pop();
        int sum = leftOperand + rightOperand;
        values.push(sum);
    }

    private int pop() {
        return values.pop();
    }
    
    public int top() {
        return values.top();
    }

    public void minus() {
        int rightOperand = pop();
        int leftOperand = pop();
        int sum = leftOperand - rightOperand;
        values.push(sum);
    }

}
